Aims: To investigate how the biopsy Gleason score (GS) and the clinical risk classification have been changed by the reporting rules.

Methods: 565 prostate biopsy specimens were reassessed. Each Gleason pattern, 1 to 5, was interpreted according to the modified Gleason grading system proposed by the International Society of Urological Pathology. The GS for each case was assigned by the previous reporting rules in the institute (OLD rules), applying the overall-scoring, and ignoring a pattern occupying less than 5% and the tertiary pattern. The GS was also assigned according to the NEW rules, applying the highest-core scoring and reflecting a pattern occupying less than 5% and the tertiary pattern.

Results: GS upgrading by the NEW rules was observed in 195 (35%) patients. Of these, 179 (92%) patients were upgraded only by applying the highest-core scoring. Of 198 patients with GS 6 by the OLD rules, 22 (11%) were upgraded to GS 3+4. Of 172 patients with GS 3+4 by the OLD rules, 59 (34%) and 28 (16%), respectively, were upgraded to GS 4+3 and ⩾8. Of 108 patients with GS 4+3 by the OLD rules, 63 (58%) were upgraded to GS ⩾8. As a result, the distribution of D’Amico’s clinical risk classification (low, intermediate and high risk) was changed from 26%, 43% and 31% to 23%, 35% and 41%, respectively.

Conclusions: Clinicians should be aware that the reporting rules, especially the highest-core scoring, contribute to a significant upward shift of the biopsy GS and risk classification.